Piezoelectric crystal holder



Feb. 2l, 1950 H. L.. sElDl-:N

PIEZOELECTRIC CRYSTAL HOLDER Filed Jan. l, 1945 Patented Feb. 21, 1950 PIEZOELECTRIC CRYSTAL HOLDER Herman L. Seiden, Chicago, Ill., assignor of onethird to Thomas C. Flanagan and one-third to Raymond T. Moloney, both of Chicago, Ill.

Application January 1, 1945, Serial No. 570,902

11 Claims.

This invention has as its principal object the provision of improvements in a holder for piezoelectric crystals of the type employed in tuning resonant circuits, particularly in conjunction with radio telephone and analogous communication equipment.

Among the principal features of novelty and utility of the invention are: a crystal holder in which the crystal components may be inserted and Withdrawn at will from a receiving pocket without the necessity of attaching or removing connecting leads; contact means associated with the receiving pocket or receptacle which give stable, pressure-contact with the crystal components when the latter are merely inserted in operative position; a holder construction, including paticularly a crystal receptacle adapted to receive crystals of different size without the necessity of altering the contact elements; a holder construction which greatly facilitates the testing A further and highly important aspect of the invention is the provision of a crystal holder having the foregoing features and which, in addition, provides a cover and base structure which can be hermetically sealed with great facility and at little expense, such sealing being of substantially permanent character, so that the frequency characteristic is stable and fully safeguarded against the heretofore troublesome effects of moisture and the like, even under most adverse atmospheric conditions.

Other objects and aspects of novelty of the invention pertain to details of the preferred construction hereinaiter described in View of the annexed drawing in which:

Fig. 1 is a perspective view of the complete crystal unit or holder;

Fig. 2 is a Vertical side section through the unit of Fig. 1;

Fig. 3 is a bottom plan view of the unit;

Fig. 4 is a transverse vertical section along lines 4-4 of Fig. 2;

Fig. 5 is a horizontal cross section looking down upon lines 5 5 of Fig. 2;

Fig. 6 is a magnified fragment in plan of a corner of one of the crystal contact plates;

Fig. 7. is a, magnified sectional fragment of the sealing region of the lower or base part of the holder;

Fig. 8 is a side section of a modified sealing means, with parts shown in elevation, to reduced scale.

Numerous expediencies have been resorted to in the art for procuring a permanent or practicable hermetic seal to protect resonating crystals against moisture; such expediencies either are not Wholly successful because the sealing is not permanent, or because they involve manufacturing procedures or materials which are too expensive or unsuited to large-scale production. Holders made according to current practices are shortlived, and must be discarded after a few weeks use in humid climate. Holders made in accordance with the present invention are permanently and effectively sealed; moreover, they are quite rugged, and the construction, in addition to the advantages heretofore recited, lends itself to economical large-scale production.

Referring to Fig. 1, the novel holder consists of a base member I0 from which project jack o1' contact connection .pins II and I2, and which is surmounted by a metal jacket or cover I3 fitted snugly against a shoulder I4 on the base. The base member I0 is formed of a special glass, as Will be referred to more particularly hereafter.

Means providing a receptacle or mounting for the crystal assembly is shown in Fig. 2, and consists of a Bakelite or other plastic or ceramic member I5 fitting at its bottom against the top I6 of the base and having in its median portions a pocket I'I, open at top and bottom, to receive the crystal I8 and (Figs. 4 and 5) fianking electrode plates I9 and 20.

The pocket Il may be enlarged as indicated by the dotted line delineation Ila, Fig. 5, to accommodate crystal assemblies of larger size, Without change in the jack .pin structure, as will now appear.

Referring to Fig. 5, the mounting member I5 is moulded with a rounded jack-pin groove 22 and 23 at each side but at opposite ends thereof, and into which the upper offset portions Ila and I2a of the jack pins II and I2 project, and in addition, there is a square grove 24 and 25 moulded in the mounting on the opposite side of the pocket from one of the grooves 22 or 23, and adapted to receive a bowed presser spring 26 or 21 (see Fig. 4 also) respectively pressing one of the electrode plates 2B or I9 against the crystal I8. It will also be observed in Fig. 5 that each of said presser springs serves to urge the opposite electrode plate against its corresponding jack pin; for example, spring'ZIi urges plate Iii against pin portion 42a, and a corresponding function obtains for spring 21 with regard to pin portion I Ia. By this means, the crystal assembly is yieldingly but positively held in the pocket I'i, with the electrode plates properly held against the crystal and making rm electrical contact with the jack pins.

Spacing ears 3i! (Figs. 6 and 5) accurately gauged in the electrode plates at the four corners thereof, serves to dispose the plates in proper spatial relation to the crystal, cooperatively with the pressure of springs 26 and 2, and in this connection it is pointed out that each of the upper pin portions Ila and I2a is iiatted las at IIJ: and IZx (Figs. 5 and 4) on the side'thereof which bears against the corresponding electrode plate, by reason of which (with the action of the presser springs) the electrode plates i9 `and 2D are firmly and accurately seated against the crystal 118, ear portions 30 vserving yto gauge 4the Yspacing of the plates relative to the Crystal, it being understood that the jack pin portions II and I2 are accurately'located in the base portion III, and that their upper portions Iglu and v Hx, and i201. and IZ, are accurately gauged to this end.

It will now appear that `with the crystal as sembly in the pocket (assuming cover or envelope I3 vto be removed) the base portion I0 may :be separated from the mounting or holding member i5 and pin portions -I'Id and I2a withdrawn therewith without disturbing the crystal or the electrode plates, lsince springs 26 Vand 21 will held the `latter in place, and accordingly` k3.' (Fig. 2) yand a presser vspring .33 therefor is placed upon the top of the holder part I5.

The cover or jacket I3 is preferably stamped `from brass 'and coated, eXteriorly at least, with a durable .corrosion-resisting plating. It is also desirable, but not essentiaLthat'the inner, lower, .edge portions of the cover be tinned, for 'reasons to appear.

With the parts assembled as described above, the cover I3 is fitted -onto the base .I', reduced as at iila, Figs. i and 7, to provide shoulder I4.

The base Ymembers Ill, as heretofore stated, are ypreferably made of special lglass of the type 'suited for electrode mounting and for glass-tom'etalsealing, the jack pin portions Il and i2 being moulded into the base portion I0 and sealed therein. On the outside portion of `the base E i3, justabove the shoulder Il?, (Fig.7) there is provided a narrow .metallic band or vnlm or plating extending entirely around the 'base Aand completely sealed thereto, such band or plating being of a metal, for example, silver, copper, and the like, adapted 'for soldering.

Whenthe cover i3 hasbeenapplied as afore-l said, it is soldered to the sealing band 35 by application of heat, as by an ordinary soldering iron, a heated clamp, or inductive device. The resulting seal, represented by the solder 36, Fig. 7, is permanently and completely moistureproof; moreover, it is of Such nature that, should necessity require, the seal may easily be broken and renewed.

In Fig. 8 there is shown a modiiied base construction in which the lower open margin or skirt MX of the metal jacket LEX. iits entirely down over a metal cup l0 having a closed bot- ,tom wall 4I in which are a pair of contact-pin openings having upwardly or `inwardly extruded collars d2; the cup portion is lled with a fired ceramic or vitreous sealing composition 43 making an air-tight seal with the cup and with the contact pins II Z and IZZ and insulating the latter from the metal cup. This base unit may be substituted for the unit It of Fig. 2, and with the elongated envelope or jacket ISX, is sealed by A.owing solder into the region between the rounded edge portions iid, provided for this purpose, on the bottom edge of the cup, and the lower skirt edges I 4X of the jacket.

The objects and advantages of the `invention `maybe realized in modications of the specific construction set forth 'for purposes of illustration, it being understood that it is the intention to include all modifications fairly coming within the scope of the appended claims.

I claim as my invention:

l. A holder for Velectrical instrumentalities comprising: a receptacle of non-conductive `material and having a pocket therein, grooves on opposite side walls of said pocket, a plurality of lat electrical instrumentalities disposed in said pocket, spring means in certain of said grooves on'opposite-sides of the vpocket and adjacent -opposits ends of the latter, .and electrical connection .means withdrawably disposed in certain other of said grooves apposite each said spring .mea-ns, whereby a turning moment is imparted to said instrumentalities to urge the same respectively against, and in electrical contact with, said connection means, said instrumentalities being firmly but yieldingly held in said pocket by action. of said springT means.

2. The invention defined in claim l further characterized in that said electrical `connection means are 'secured in a base member and are slidable into and out of operative engagement in said receptacle, as a unit.

3. The invention deiined in claim l further characterized bythe provision of a metal envelope fitted around said receptacle and hermetically sealed by metallic sealing metalically joined to a metallic sealing surface plated :on said non-metallic material.

4. The invention defined in claim l and further characteriaed in that said lelectrical connection means are secured in abase member of non-conductive material and are slidable into and out of operative engagement in said Vreceptacle as a unit, and further characterized in that a metal envelope is :ntted around said receptacle and at least a yportidn of said base'member, said base member having a metallic .sealing surface hermetically sealed thereto by plating thereon, said envelope being sealed to said surface by a metallic sealing substance fluXedly engaged as by soldering with the envelope and said sealing surface.

5. A .piezo-electric crystal `unit comprising a receptacle of .non-conductive material having a pocket therein, a pair of electrode plates disposed in said pocket with a crystal therebetween, contact means on each side of said pocket and spaced apart on opposite sides of the median region of said plates and crystal and each contacting one of said plates, yieldable presser means in the form of bowed leaf spring each communicating into said pocket on sides thereof opposite each said contact means and respec tively pressing against one of said plates in a direction towards the contact means on the opposite side of the pocket, whereby said assembly of plates and crystal is yieldingly held within said pocket, and each said plate is urged into contact with one of said contact means, and whereby said contact means may be withdrawn slidably with said assembly remaining in the pocket.

6. In a piezo-electric crystal unit, a holder having a chamber therein, a crystal assembly, including a pair of electrode plates having a piezo-electric crystal therebetween, and disposed in said chamber, contact pins insertable into said chamber and oiTset such that at least one of said pins is contactingly engaged with one of said plates on opposite sides of the crystal, and spring means housed in elongated grooves in the Walls of said chamber and urging said assembly such that corresponding plates engage their respective contact pins, said contact pins being insertable and withdrawable at will.

7. The invention defined in claim 6 further characterized in that said contact pins are disposed in a mounting, and in addition to being offset with respect to each other, as aforesaid, are each offset themselves with opposite end portions projecting from said mounting, one pair of corresponding end portions being set at a predetermined distance apart for contacting engagment as aforesaid with a predetermined minimum size of said plates, and with larger plates extending beyond said minimum size at least in the direction in which said contacting engagement portions are set apart, the remaining end portions of said pins being set apart by oifset as aforesaid a predetermined distance for engagement with complementary connection means.

8. In a crystal holder of the class described, contact pins set in a mounting with opposite end portions projecting in substantial parallelism on opposite sides of the mounting, one pair of said end portions being set apart a predetermined distance for engagement With complementary contact means, the remaining pair of said end portions being ofl'set relative to a plane therebetween to receive planar crystal elements there.

between, said last-mentioned end portions also being oiTset relative totheir respective opposite end portions for disposition a predetermined minimum distance apart for operative engagement with a predetermined minimum size of said crystal elements, and also with crystal elements longer in the direction of said minimum distance than said minimum size.

9. In a crystal holder of the class described, a nat crystal element, a plurality of contact pins set in a mounting with connection terminals spaced apart on one side of said mounting a rst predetermined distance and with opposite p0rtions projecting in approximate parallelism from the opposite side of Hsaid mounting and spaced apart av-second predetermined distance less than said rst distance,-'and also offset on opposite sides of a plane to contain said crystal element such that one of each of said last-mentioned end portions will be disposed on opposite sides, relatively, of said crystal element, and such that said crystal element may be of different sizes greater than said second predetermined distance, said offset end portions being thereby adapted to cooperate electrically with said first-mentioned crystal and with said crystals of greater size.

l0. In a piezo-electric crystal holder, the combination with a flat crystal assembly of a casing having opposite wall portions facing opposite sides of the flat crystal assembly disposed therein, a pair of elongated grooves in each of said wall portions each having a longitudinal side opening toward said assembly, an elongated bowed leaf spring in one of said grooves on each side of said assembly but respectively disposed near opposite extremities of said `assembly and exerting opposing pressures on the assembly in a manner to exert a turning moment on the latter, and a pair of elongated contact members mounted in a companion member for said casing and respectively offset to have a contact portion disposed in one of said grooves on, and in contact with, opposite sides of said crystal assembly on sides of the latter opposite to the sides thereof engaged by said springs, whereby said springs urge said crystal assembly into electrical contact with said contact portions and the latter may be slidably disengaged from the assembly with said springs holding the assembly in the casing.

11. A holder for piezo-electric crystals and comprising an insulation body having a pocket therein with oppositely disposed wall portions, a flat crystal means in the pocket with opposite faces each confronting one of said Wall portions, a pair of elongated grooves in each said wall portion and extending in parallelism with said faces, each groove having a longitudinal side opening toward the face of the crystal means opposite thereto, an elongated contact member in one said groove on each side of the crystal means but respectively near opposite ends of the crystal means, and an elongated spring element in a. said groove on each side of the crystal means and pressing the latter respectively toward one of the contact members engaged with the side of the crystal means opposite thereto, means insulatingly mounting said contact members for movement jointly into and out of their respective grooves in said body pocket, said spring elements maintaining the crystal means in the pocket notwithstanding movement of said contact members into and out of their grooves as aforesaid, and further pressing said crystal means into good electrical contact with -said contact members when the latter are disposed in their grooves.

HERMAN L. SEIDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,329,497 Washburn Sept. 14, 1943 2,329,498 Washburn Sept. 14, 1943 2,384,757 Kuenstler Sept. 11, 1945 2,430,478 Nelson Nov. 11, 1947 FOREIGN PATENTS Number Country Date l544,334 Great Britain Apr. 29, 1942 

